"Where there has been an overpayment of any tax imposed by this Chapter for any income year, the amount of such overpayment may be credited against any due and unpaid liability in respect of any tax imposed under this Title on the taxpayer who made the overpayment, and the balance shall be refunded to such taxpayer."

Section 2. The introductory paragraph of Subsection (6) of Section 1903(b) Chapter 19, Title 30, Delaware Code, is amended to read as follows:

"(6) If the entire business of the corporation is transacted or conducted within this State, the remainder of its entire net income shall be allocated to this State. If the business of the corporation is transacted or conducted in part without this State, such remainder, whether income or loss, shall be apportioned to this State on the basis of the ratio obtained by taking the arithmetical average of these 3 ratios."